Study of the Atmospheric Degradation, Radiative Forcing and Global Warming
Potentials of CH2FCH2OH, CHF2CH2OH and CF3CH2OH
S. R. Sellevåga, G. Myhreb, J. K. Sundetb and C. J. Nielsena
a
b
Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, 0315 Oslo, Norway
Department of Geophysics, University of Oslo, P.O. Box 1022 Blindern, 0315 Oslo, Norway
INTRODUCTION
This work is a part of the project “Impact of Alternative Fluorinated Alcohols and
Ethers on the Environment (IAFAEE)”, which is a co-operation between University of Oslo, University College Dublin, University of Crete and Russian
Academy of Science. We have studied the atmospheric degradation, radiative
forcing and global warming potentials (GWP) of CH2FCH2OH, CHF2CH2OH and
CF3CH2OH, which have been suggested as new CFC and HCFC replacements.
See also posters AP6 and AP12.
RESULTS
Rate Constants for the Reactions with OH Radicals
1.6
1.4
y = (-0.017±0.049) + (5.907±0.448) * x
y = (0.0058±0.0050) + (1.878±0.023) * x
1.2
ln {[CHF2CH2OH]0/[CHF2CH2OH]t}
ln {[CH2FCH2OH]0/[CH2FCH2OH]t}
1.4
1.2
1.0
0.8
0.6
0.4
0.2
1.0
0.8
0.6
0.4
0.2
0.0
0.0
0.00
0.04
0.08
0.12
0.16
0.20
0.24
0.28
0.0
0.1
0.2
ln {[CH3CH3]0/[CH3CH3]t}
ln {[CF3CH2OH]0/[CF3CH2OH]t}
0.3
0.4
0.5
0.6
0.7
ln {[CH3CH3]0/[CH3CH3]t}
y = (0.0065±0.0049) + (0.513±0.025) * x
0.20
0.16
0.12
0.08
0.04
Fig. 4. Geographical distribution of radiative forcing due to CF3CH2OH. The global mean radiative forcing is 0.17 W m-2. Similar to the well mixed greenhouse
gases the largest radiative forcing is in tropical regions with small cloud amounts,
high surface temperature, and a large temperature difference between the surface
and the tropopause.
0.00
0.0
0.1
0.2
0.3
0.4
ln {[CH3CH3]0/[CH3CH3]t}
Fig. 1. Loss of reactant versus reference in the reaction with OH.
Table 2. Atmospheric lifetimes based on the OH reaction rate
constants from this work.
Compound
Lifetime/days
CH2FCH2OH
8.0
CHF2CH2OH
19.3
CF3CH2OH
71.0
Table 1. Rate constants for the OH reactions with CH2FCH2OH,
CHF2CH2OH, and CF3CH2OH at 298 K.
CF3CH2OH
CHF2CH2OH
CH2FCH2OH
k/1013 cm3 molecule1 s1
1.28  0.06
1.1  0.1
0.955  0.071
1.07  0.05
0.986  0.041
0.968  0.023
4.70  0.06
3.6  0.3
14.8  1.1
11.3  0.9
Method
RR
RR
FP-RF
DF-LIF
LP-LIF
FP-LIF
RR
RR
RR
RR
Reference
This work
[1]
[2]
[3]
[3]
[3]
This work
[1]
This work
[1]
Table 3. GWP values relative to CO2 and CFC-11 for three time horizons.
20
Compound
CH2FCH2OH
CHF2CH2OH
CF3CH2OH
0.9
0.4
CH2FCH2OH
0.8
CHF2CH2OH
0.7
Absorption cross section
-18
2
-1
/(10 cm molecule )
0.3
0.2
0.1
3000
2500
2000
1500
Wavenumber/cm
1000
500
METHODS
The relative rate measurements were performed in synthetic air at 1013  15 hPa and 298  2 K
in a 250 L smog chamber with in situ FTIR detection. Hydroxyl radicals were generated by
photolysis of ozone/water mixtures. Typical volume fractions were: 5-10 ppm of each organic
compound and ca. 103 ppm of both water and ozone.
The measurements of absolute integrated absorption intensities were carried out at 298  2 K
using a Bruker IFS 113v spectrometer and DTGS detectors. A Ge/KBr beamsplitter was used in
the MIR region, while 3.5 μm Mylar film was used in the FIR region. Single channel spectra of
pure vapours were recorded in the region 4000-70 cm-1 with 1.0 cm-1 resolution and adding 512
scans. The pressures of the samples were in the range between 2 and 20 hPa, and were measured
using a MKS Baratron Type 122A pressure gauge.
The atmospheric distributions of CH2FCH2OH, CHF2CH2OH and CF3CH2OH were calculated using the Oslo CTM2 model, which is an off-line chemical transport/tracer model. The
model uses pre-calculated transport and physical fields to simulate chemical turnover and distribution in the atmosphere. It is valid for the global troposphere and is three-dimensional with the
model domain reaching from the ground up to 10 hPa (see e.g. ref. [4] for a further description).
The radiative forcing calculations were carried out using a thermal infrared broad band model
(details of the model are given in ref. [5]). CH2FCH2OH, CHF2CH2OH and CF3CH2OH were
included with 5, 6 and 8 bands, respectively.
0.3
0.2
0.1
4000
3500
3000
2500
2000
1500
Wavenumber/cm
1000
-1
2.0
CF3CH2OH
Absorption cross section
-18
2
-1
/(10 cm molecule )
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
4000
3500
3000
2500
2000
500
CFC-11
0.00022
0.00112
0.00411
0.4
-1
1.8
CO2
0.354
1.831
6.719
0.5
0.0
3500
CFC-11
0.00060
0.00312
0.01146
0.6
0.0
4000
CO2
3.836
19.83
72.78
Time horizon/year
100
CO2
CFC-11
1.140
0.00024
5.894
0.00126
21.63
0.00461
CONCLUSIONS
The impact of CH2FCH2OH, CHF2CH2OH and CF3CH2OH on the Earth's
radiative balance is negligible. With a lifetime of 71 days, however, a large
part of CF3CH2OH will enter into droplets and end up as TFA.
Absorption Cross Sections
Absorption cross section
-18
2
-1
/(10 cm molecule )
Radiative Forcing and Global Warming Potentials
Fig. 3. Zonal mean vertical
distribution of CF3CH2OH
given in ppt. The abundance
decrease much faster with
altitude than for well mixed
greenhouse gases but to a
smaller extent than for the
two other compounds in
this study.
1500
Wavenumber/cm
1000
500
-1
Fig. 2. Absorption cross sections (base e) of pure vapors of CH2FCH2OH,
CHF2CH2OH and CF3CH2OH.
500
[1] Kelly, T., Sidebottom, H., Unpublished.
[2] Wallington, T.J., et al. (1988) J. Phys. Chem. 92, 5024-5028.
[3] Tokuhashi, K., et al. (1999) J. Phys. Chem. 103, 2664-2672.
[4] Acerboni, G., et al. (2001) Atmos. Environ. 35, 4113-4123.
[5] Myhre, G., Stordal, F. (1997) J. Geophys. Res. 102, 11181-11200.